Wood is a natural raw material, and would hardly be considered a risk to the environment. However, the handling of wood materials on an industrial scale has been shown to have a negative impact on water bodies that run-off from industrial sites that process wood-based materials. Most investigations related to water pollution from wood-based industries have focused on large industrial sites such as pulp and paper mills. The goal of the present thesisis to understand better such environmental problems and treatment solutions that occur at most wood handling sites. Where there are large outdoor storage areas for logs and sawdust that are exposed to rainfall or irrigation, such as the wooden-floor and bio-energy sectors. Leachate generated by the contact of water with wood in storage areas contains a large amount of organic matter that is potentially hazardous to water bodies that receive run-off from the site.

It has been found that different wood species yield different leachate compositions, with leachate from oak having the highest pollutants content, followed by leachate from pine. This investigation shows that oak has the potential to leach about 10 times the amount of polyphenols compared with other investigated species (i.e., pine, beech and maple). Furthermore, oak leachates have the lowest ratio of biological oxygen demand at 7 days tochemical oxygen demand (0.12), which suggests a potential problem with the biological degradation of this leachate. It has also been shown that leachate from wood are potentially toxic to aquatic organisms.

Treatability studies with the aim of reducing the environmental impact of wood leachate were conducted on a pilot scale as part of the scope of this thesis. The results showed, among other options, the possibility of using constructed wetlands to treat leachate. It was found that plants and aeration can affect the performance of a wetland. However, the most important factor is the time water spends in the wetland. Filter material that could be used to absorb leachate was also studied. A filter consisting of a mixture of peat and ash (from incinerated organic matter), was used to absorb a specific chemical group (polyphenols) in the leachate. It was also shown that polyphenols are vulnerable to ozone, representing a third viable treatment process.

This study investigated the effects of aeration and/or vegetation in experimental constructed wetlands (CWs) as mesocosms on the removal of pollutants in oak wood leachate. Twelve outdoor wetland mesocosms, with randomized replicated treatment combinations of vegetation (Phragmites australis) and aeration was monitored during the second and third year after construction. The investigation included control tanks with no aeration and no vegetation. The parameters monitored were polyphenols (PPs), chemical oxygen demand (COD) and water colour. The reduction of COD after 28 days was approx. 50% and more than 50% of PPs, whereas only 40% of the water colour was removed. Aeration increased the effect of both COD and PP removal. The vegetation treatment had a small but significant effect on removal of COD. The vegetation + aeration treatment, as well as aeration alone, increased the removal efficiency of COD from 9.5 g m(-3) d(-1) in the control to 11 g m(-3) d(-1). The results suggest that CWs can be used to treat stormwater contaminated by oak wood leachate. Further, it is suggested that the main processes for removal of pollutants in the leachate occur in the open-water habitat and that the hydraulic retention time is more important for removal than aeration and vegetation related processes.

In the present study, we investigated the possibility of treating oak wood leachate with a combined ozone and biological treatment. Wood leachate is characterized by high amounts of organic carbon and is reported as being toxic to aquatic organisms. Ozone was used as a pre-treatment before using aerobic degradation. The biological treatment was applied for seven days and evaluated using head-space respirometry. Target pollutant in this investigation was polyphenols in combination with more general parameters, such as chemical oxygen demand (COD), total organic carbon (TOC) and colour. A custom made bubble column reactor was used, 1.5 L of wood leachate was exposed to 0-4 g/L of ozone, corresponding to a specific ozone dose between 0.7-7 g/L O-3/g of initial COD. Oak wood leachate was found to be easily degraded by ozone, with >90% of polyphenols degraded. COD was degraded by 73%, TOC by 61% and colour by 97% by ozone. Furthermore, a positive correlation between biodegradation and ozone pre-treatment was found.

The efficiency of biological treatment systems in degrading organic matter is affected by both the available nutrients and the efficiency of the microbial organisms that carry out the degradation. This study assesses whether a wetland treatment system treating stormwater from a wood industrial site faced nutrient deficiency or lacked efficient microbes, and whether addressing these possible problems could enhance the degradation of organic matter in the system. The stormwater was a mix of industrial stormwater, irrigation water and leachate from woodchip piles. The industry mainly processes pedunculate oak, which is known to create a leachate high in polyphenols. This water is currently treated in a pilot-scale wetland system and an aerated lagoon. To study whether the treatability could be enhanced by addition of nutrients (phosphorus, nitrogen, micronutrients), headspace respirometry was used. The effect of adding microbes from a paper mill activated sludge system was also evaluated. Our results showed that all nutrient additions had a positive effect on the treatability of the stormwater. In particular, the addition of nitrogen showed a 12% rise in chemical oxygen demand reduction over 336h. However, addition of paper mill activated sludge did not enhance the degradation of organic matter; instead, a toxic effect of the stormwater was shown.

Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.

Marques, Marcia

Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science. Department of Sanitary and Environmental Engineering Rio de Janeiro State University-UERJ Rio de Janeiro Brazil.

Batch tests were carried out with sawdust obtained from oak (Quercus robur), maple (Acer platanoides), pine (Pinus sylvestris), beech (Fagus sylvatica) and wood chips from oak and pine. Leaching of organic compounds expressed as dissolved organic carbon (DOC) in mg/kg of dry mass took place during the first 24 h. The following additional variables were analysed: pH, conductivity, colour, phenols, tannins and lignin, and biochemical oxygen demand (BOD7). When leachates obtained with oak wood chips and pine wood chips were compared, no significant difference was observed. However, in batch tests with sawdust, DOC released by oak (90 000 mg/kg) was significantly higher (P = 0.0001) than DOC released by pine (30 000 mg/kg). The results suggest that particle size is not the only variable affecting the leaching of organic compounds from wood. Regarding BOD, colour [platinum-cobalt (Pt-Co)], phenols, tannins and lignin, the leaching patterns differed among species, and oak was the species with the highest released values.

In the present study, two combinations of filter materials in filter/columns were examined for removal of total organic carbon (TOC) and polyphenols (PP) found in storm water runoff from wood storage areas in a wooden floor industry. One filter/column was packed with peat mixed with carbon-containing fly ash, while another filter/column contained only peat (without ash). The mixture of peat and ash has shown faster and higher removal capacity for TOC and faster removal with the same final removal capacity for PP (in grams of pollutant per kg of sorbent) at the saturation point. The superiority observed for the peat and ash filter is presumably due to the unique characteristics of peat and ash, which enhanced the treatment efficiency when used together in a mixture. Based on the observed results, filters formed by peat and carbon-containing ashes proved to be a potentially low-cost option for the treatment of storm water generated at storage areas of wood materials such as logs, sawdust and wood chips.

Abstract: In this study, leachates resulting from leaching tests carried out with sawdust from five tree species were investigated. The studied species were: Pedunculate oak (Quercus robur), Scots pine (Pinus sylvestris), European larch (Larix decidua), Norway spruce (Picea abies) and European beech (Fagus sylvatica). The analyses included chemical parameters such as pH, TOC and phenolic compounds (reported as total poly-phenols) and acute toxicity on two different organisms, the crustacean Artemia sauna and the bacteria Vibro fischeri (Microtox (R)). There are very high amounts of different phenolic compounds in the leachate, and large differences between tree species. The leachates produced by sawdust and bark of different tree species presented great variation regarding acute toxicity. V fischeri was more sensitive than A. sauna and leachates from pine sawdust and pine bark produced the highest toxicity response from V fischeri. This study indicates that bark is one component of the tree anatomy that needs to be handled as a potential hazardous material to the aquatic environment. The large variation in toxicity presented by different tree species need to be taken into account when assessing the impacts to surrounding watercourses and constructing wastewater treatment facilities for the wood-based industry such as irrigation water, stormwater runoff from storage areas.